To create greater improvements in aerobic fitness, participants are required to exercise at high levels of VO2peak (e.g. ≥80% VO2peak). High intensity interval training (HIIT) requires participants to exercise at high levels of VO2peak (≥80% VO2peak) for short periods (e.g. 15 seconds) followed by a recovery (active or passive) and typically continue this pattern for 30 minutes or until exhaustion.